Just as the Trump administration is preparing to seek repeal of a long-disputed Obama-era clean water regulation, a conservative legal group is suing the Environmental Protection Agency to obtain documents it says demonstrate that EPA illegally used a social media platform for “propaganda” in defending the rule.

Judicial Watch on June 21 filed a complaint in U.S. District Court saying EPA had failed to respond to an earlier Freedom of Information Act request for documents relating to the agency’s use of the social media platform Thunderclap to promote the “Waters of the United States” regulation. That rule was finalized in 2015 under the EPA and Army Corps of Engineers, but was immediately challenged in court as burdensome by states and industry.